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By Kristie Sullivan, M.P.H., and John J. Pippin, M.D.
ALTERNATIVES TO ANIMAL RESEARCH
Chimp Genome Project Shows Tiny Difference Makes All the Difference
Employing the results of the recently completed Chimp Genome Sequencing Project, researchers at the University of California San Diego have linked human-chimp genetic differences to two important species-specific disease findings. One is the discovery of the first human-specific protein that is also expressed in brain cells associated with human brain diseases that do not occur in chimps, such as Alzheimer’s disease, multiple sclerosis, and HIV-related dementia. The second is a single oxygen atom difference that makes humans and chimpanzees resistant to each other’s malarial parasites.
Says Ajit Varki, M.D., coauthor of both studies, “Chimpanzees have long been thought of as a model for studying human diseases. In fact, what is most remarkable is that many of our diseases are rather different, either in incidence or in severity.” If a single oxygen atom difference can convey malaria resistance, it’s small wonder that chimp research is such a poor surrogate for human studies.
Hayakawa T, Angata T, Lewis AL, et al. A human-specific gene in microglia. Science. 2005;309:1693.
Martin MJ, Rayner JC, Gagneux P, et al. Evolution of human-chimpanzee differences in malaria susceptibility: relationship to human genetic loss of N-glycolylneuraminic acid. PNAS. 2005;102:12819-12824.
New Cells Allow Cruelty-Free Drug Testing
St. Paul, Minn.-based biotechnology company BioE has become the first company to produce and market multilineage progenitor cells (MLPCs) from human cord blood. These stem cells are isolated from umbilical cord blood after birth, and scientists can coax the cells into at least nine different cell types: fat cells, three different types of nerve cells, liver and pancreas precursor cells (which could then be differentiated into hepatic or pancreatic cells), muscle cells, blood vessel wall cells, and bone cells. Drug and chemical companies can use these progenitor cells, and their derived descendant cells, to test the metabolism and toxicity of new compounds in the species of interest—humans. Researchers can gain a better knowledge of the biochemical and genetic characteristics of human cells—which is important for cancer and other disease research—and develop potential tissue and gene therapies for diseases that attack these organs.
Interested researchers can find out more at www.bioe.com.
Fewer Dogs and Cats Used in Experiments
Since 1973, the number of dogs, hamsters, cats, guinea pigs, and rabbits used in experiments has decreased by at least 40 percent, according to the recently released 2004 USDA Animal Care Report. But the number of primates used has increased by 30 percent—up to 54,998—as has the number of farm animals, up 58 percent since 1990, when use of these animals was first reported.
The report did not include figures on rats, mice, birds, or reptiles—who are involved in 95 percent to 99 percent of experiments but are not counted by the USDA or covered by the Animal Welfare Act. Recent reports estimate the number of rats and mice used in laboratories at 80 million to 100 million, and that figure is increasing every year.
USDA Animal Care Report Fiscal Year 2004. APHIS Web site. Available at: http://www.aphis.usda.gov/ac/awreports/awreport2004.pdf. Accessed Feb. 24, 2006.
Carbone, L. What Animals Want. New York, NY: Oxford University Press; 2004:25-28.
By Dulcie Ward, R.D., and Susan Levin, M.S., R.D.
Calcium Supplements Don’t Reduce Fracture Risk
Calcium and vitamin D supplementation did not significantly reduce the incidence of fractures in a recent study. The 36,282 postmenopausal participants enrolled in the Women’s Health Initiative clinical trial were given either a supplement containing 500 milligrams of calcium plus 200 IU vitamin D or a placebo daily. Hip fractures were 12 percent less frequent in the supplemented group, but that result was considered to have been attributable to chance. The supplemented group had no reduction in vertebral fracture, fracture of the lower arm or wrist, or total fractures. There was also a 17 percent increase in kidney stone formation among the supplemented group. The results reinforce earlier studies showing that increased calcium intake does not necessarily mean stronger bones and better health. Other factors that seem to play a more important role in bone health include sodium intake, smoking, physical activity, and intake of animal protein, which leaches calcium from the bones.
Jackson RD, LaCroix AZ, Gass M, Wallace RB, Robbins J, Lewis CE, et al. Calcium plus vitamin D supplementation and the risk of fractures. N Engl J Med. 2006;354:669-683.
Dairy Products Fail to Stop Weight Gain
A new study from Harvard’s Health Professionals Follow-up Study gives no support to the advertising claim that milk helps control weight. In a group of 51,529 men ages 40 to 75, those who consumed the most calcium or dairy products at the study’s onset gained the same amount of weight as those who consumed the least.
In an unadjusted analysis, men who increased their calcium or dairy intake during the study seemed to gain slightly less weight (approximately a 1-pound difference over a 12-year period). However, when the results were controlled for smoking, exercise, fruit and vegetable intake, fiber intake, and other confounders, the apparent benefit of calcium and dairy products disappeared. This suggests that, in studies implying that calcium or dairy products protect against weight gain, it is actually other healthy lifestyle factors that are responsible for weight control.
Rajpathak SN, Rimm EB, Rosner B, Willett WC, Hu FB. Calcium and dairy intakes in relation to long-term weight gain in US men. Am J Clin Nutr. 2006;83(3):559-566.
Obesity Decreases Chance of Surviving Breast Cancer
In a study in Shanghai, China, investigators followed a group of 1,455 women with breast cancer. They found that being overweight at or soon after diagnosis of breast cancer was related to a decrease in chance of survival and disease-free survival. This is one of only a few studies to look at weight’s effect on breast cancer in an Asian population. Most Asian women are slim by Western standards. After a five-year follow-up, the survival rates were higher for those with the lowest body mass index (BMI), a measure of body weight adjusted for height. The lowest BMI group had an 86.5 percent survival rate, while the highest BMI group had an 80.1 percent survival rate. Corresponding disease-free rates were 81.9 percent for the lowest BMIs and 76.6 percent for the highest. Excessive adipose tissue, which increases hormonal activity and stimulates cell growth, may be what promotes the tumor development and metastasis. The results support previous findings that weight control can have a substantial effect on incidence and survival of breast cancer.
Tao MH, Shu XO, Ruan ZX, Gao YT, Zheng W. Association of overweight with breast cancer survival. Am J Epidemiol. 2006;163:101-107.